Mars : Past and Present

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The dusty-red sphere now called Mars has fascinated stargazers since the dawn of humanity, but Earthlings’ view of the planet has changed drastically over the years. Once thought of as a lush alien world teeming with life, it was later dismissed as an arid, desolate orb. But now, scientists have announced the Red Planet has long, fingerlike strips of seeping, salty, liquid water that just might aid in the search for extraterrestrial life.

The finding, revealed Monday (Sept. 28) by NASA scientists, once again changes the way people view the bright-red planet, The Red Planet experts told Live Science.

The ancient Greeks and Romans named The Red Planet—a planet barely more than half Earth’s size—after the god of war. But they likely didn’t realize it was another world, with two moons to boot, said Bruce Jakosky, a professor of geological sciences at the University of Colorado Boulder. Is Water Flowing on Mars?

In the 1600s and 1700s, astronomers tinkered with nascent telescopes and discovered that The Red Planet, like Earth, was a planet and had a roughly 24-hour day-and-night cycle. At this time, people assumed intelligent beings were scampering over the Martian surface, Jakosky said.

Early astronomers had other fanciful, and often mistaken, views of The Red Planet. In 1784, the British astronomer Sir William Herschel wrote that the dark areas on The Red Planet were oceans, and the light areas land. He also speculated the planet was home to aliens, who “probably enjoy a situation similar to our own,” according to NASA. (He also apparently thought intelligent life was living under the sun’s surface in a cool spot, NASA reported.)

In 1877, Italian astronomer Giovanni Schiaparelli reported seeing grooves or channels on The Red Planet with his telescope. Schiaparelli called these features “canali,” which can mean “natural channels” in Italian. The word was mistakenly translated into “canals” in English, a phrasing that suggested handiwork by living beings. American businessman and astronomer Percival Lowell popularized the idea, and wrote three books about aliens that likely created the canals to survive on a drying planet.

“The canals were an attempt, [Lowell] thought, by intelligent beings to carry water from the poles, where there was water, to the rest of the planet,” said Richard Zurek, chief scientist for the The Red Planet Program Office at NASA’s Jet Propulsion Laboratory in Pasadena, California.

It wasn’t until NASA’s Mariner space missions in the 1960s and 1970s that researchers could confidently prove there were no alien-made canals, Zurek said.

“We almost went to the other extreme, because we saw a hilly, cratered landscape on the first flybys of the planet,” Zurek told Live Science, referring to the Mariner 4 mission. “That suggested it was more like the moon than it was like the Earth.”

Until then, scientists had speculated that The Red Planet had a thick atmosphere that could trap heat and help the planet support life at its distant location from the sun. The Red Planet orbits at about 142 million miles (229 million kilometers) from the sun, compared with Earth’s 93-million-mile (150 million km) leap from the sun. But this wasn’t the case; The Red Planet’ atmosphere is about 100 times thinner than the gas layer surrounding Earth, partially explaining why Mars is such a cold, barren place, Jakosky said.